Deconvolution of quasar images from point-spread function: Application to 3C 273, PKS 2135+147, and PKS 0812+020

The photometric structure of the resolved quasars 3C 273, PKS 2135+147, and PKS 0812+020 has been restored by an effective deconvolution procedure from observed photographic profiles and PFSs given by Wyckoffet al. (1981). Three well-defined components have been found in quasars: (1) the central point-like source, containing about 75% of the total light, (2) an intermediate region of about 10 kpc radius, whose luminosity seems to depend on the quasar's absolute luminosity, and (3) an external region with dimensions and behaviour of the brightness profile typical of giant elliptical and cD galaxies. The apperance of the photographic images of quasars with underlying nebulosities is discussed on the grounds of reliable extended PFSs and distances. An extensive discussion is devoted to the numerical aspects of deconvolution, which belongs to the class of ill-posed inverse problems. The regularization method, which avoids the numerical instabilities arising in such problems as well in the estimation of many nonlinear parameters is also described.